Conventionally, a card reader has been widely utilized as a magnetic recording medium processing device in which reading of magnetic data recorded in a card-shaped magnetic recording medium as a magnetic recording medium (hereinafter, referred to as a “card”) and/or writing of magnetic data to a card are performed. This type of a card reader is, for example, mounted and used in a host apparatus such as an ATM (Automate Teller Machine) which is installed in a financial institution such as a bank. Further, in an industry such as a financial institution where a card reader is utilized, illegal acquisition of magnetic data of a card by a fraudulent person who attaches a magnetic head to a front side of a card insertion part of a card reader, in other words, so-called skimming has conventionally become a large issue.
In order to cope with the issue, a card reader has been conventionally proposed which is provided with a magnetic field generator structured to generate a disturbing magnetic field for disturbing reading of magnetic data of a card by a magnetic head for skimming (hereinafter, referred to as a “skimming magnetic head”) which is attached to a front side of a card insertion port (see, for example, Patent Literature 1). In the card reader described in Patent Literature 1, a technique is disclosed that a magnetic field (magnetism) generator is provided in a card insertion port of the card reader and reading of magnetic data of a card of a user by a skimming magnetic head is disturbed by a disturbing magnetic field (magnetism) generated from the magnetic field (magnetism) generator.
In this technique, a structure in which a power supply for a coil (inductor) is driven by a transistor having a switching function is adopted as a circuit for generating a disturbing magnetic field.
In the card reader shown in Patent Literature 1, the above-mentioned magnetic field (magnetism) generator is operated as follows. A fraudulent person attaches a skimming magnetic head which is a magnetic head and a magnetic reading circuit to a card insertion port of a card reader for reading magnetic data of a card. In order to prevent the skimming magnetic head from reading magnetic data, a disturbing magnetic field is generated toward the skimming magnetic head.